EP4076015B1

EP4076015B1 - Method and system to produce a sheet of material containing alkaloids

Info

Publication number: EP4076015B1
Application number: EP20812345.5A
Authority: EP
Inventors: Michele DEL BORRELLO
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2019-12-18
Filing date: 2020-11-30
Publication date: 2023-10-18
Anticipated expiration: 2040-11-30
Also published as: JP2023509335A; WO2021121931A1; BR112022011575A2; PL4076015T3; CN114980755A; KR20220116453A; EP4076015A1; US20230025967A1; EP4076015C0

Description

This invention relates to a method and system for producing a cast sheet of a material containing alkaloids.
In particular, the material containing alkaloids is a homogenized tobacco material, preferably used in an aerosol-generating article such as, for example, a cigarette or a "heat-not-burn" type tobacco containing product.
Today, in the manufacture of tobacco products, besides tobacco leaves, also homogenized tobacco material is used, like cast leaf or reconstituted tobacco.
In a "heat-not-burn" aerosol-generating article, an aerosol-forming substrate is heated to a relatively low temperature, in order to form an aerosol but prevent combustion of the tobacco material.
The homogenized tobacco material is produced by mixing different components, including tobacco powder, to form a tobacco slurry. Further, the slurry commonly contains fibres, such as cellulose fibres, in addition to those contained in the tobacco. This slurry is then stored in tanks before being sent, through a suitable delivery system, to a casting system where it enters a "casting box" to be cast on a moving conveyor steel belt and then dried into a dryer.
US 5 499 636 A discloses a method for manufactoring a tobacco web comprising a base web and a layer of tobacco material. The base web is produced by mixing slurried tobacco fiber with slurried stenghtening agent and casting the slurried mixture onto a web forming apparatus. A dispersion of tobacco material is applied along the base web to form a sheet of the tobacco web.
There is a need for a process to obtain an alternative material containing alkaloids which can be used for heat-not-burn products.
In an aspect, the invention relates to a method for the production of a sheet of a material containing alkaloids, the method comprising the steps of providing a slurry including a material containing alkaloids, an aerosol former and water; and extruding the slurry. The method also includes the step of collecting the extruded slurry in a tank having a plurality of outlets and providing more than one substrate sheet including fibres. The method also comprises the step of supplying the slurry from the plurality of outlets so as to form a plurality of strips of slurry on the more than one substrate sheet including fibres, to form more than one sheet of material containing alkaloids.
The invention also relates to a system for the production of more than one sheet of material containing alkaloids, the system comprising: more than one bobbin of a substrate sheet including fibres. The system also includes an apparatus for supplying slurry to the more than one substrate sheet including fibres. The apparatus comprises: an extruder adapted to extrude a slurry; a tank having a plurality of outlets adapted to contain the slurry; and a moving element adapted to move the more than one substrate sheet including fibres unwound from the more than one bobbin along a transport direction and under the outlet, so that slurry is applied to the more than one substrate sheet.
The slurry is supplied to a substrate sheet which includes fibres to form a sheet of material containing alkaloids. A "fibres' substrate" for the slurry is thus already present and there is no need to add a high amount of fibres in the slurry to obtain a sheet of a material including alkaloids with a relatively high tensile strength. This aspect may allow to use less water in the slurry and thus also less energy in drying the resulting sheet of a material containing alkaloids.
As used herein, the terms "sheet" denotes a laminar element having a width and length substantially greater than the thickness thereof.
As used herein, the term "slurry" denotes a liquid-like, viscous or pasty material that may comprise an emulsion of different liquid-like, viscous or pasty material. The slurry may contain a certain amount of solid-state particles, provided that the slurry still shows a liquid-like, viscous or pasty behavior.
In the following, with the term "upstream" or "downstream", reference is made to the direction of flow of the slurry.
As used herein, the term "movable support" denotes any means comprising a surface adapted to be moved in at least one longitudinal direction. The movable support may form a closed loop so as to provide an uninterrupted transporting ability in one direction. However, the movable support may be moved in a reciprocating way as well. The movable support may include a conveyor belt. The movable support may be essentially flat. The movable support may show a structured or an unstructured surface. The movable support may comprise a sheet-like movable and bendable band. The band may be made of a metallic material, including but not limited to steel, copper, iron alloys and copper alloys, or of rubber.
"Substrate sheet including fibres" denotes a sheet used as a substrate for the slurry and formed in a material including fibres. The material in which the sheet is formed may include any type of fibres, for example cellulose fibres. The sheet of a material may be placed on top of a movable support or it may be self-supporting.
A "material containing alkaloids" is a material which contains one or more alkaloids. The alkaloids may comprise nicotine. The nicotine may be found, for example, in tobacco.
Alkaloids are a group of naturally occurring chemical compounds that mostly contain basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar structure are also termed alkaloids. In addition to carbon, hydrogen and nitrogen, alkaloids may also contain oxygen, sulfur and, more rarely, other elements such as chlorine, bromine, and phosphorus.
Caffeine, nicotine, theobromine, atropine, tubocurarine are examples of alkaloids.
As used herein, the term "homogenized tobacco material" denotes material formed by agglomerating particulate tobacco, which contains the alkaloid nicotine. The material containing alkaloids can thus be a homogenized tobacco material.
The most commonly used forms of homogenized tobacco material is reconstituted tobacco sheet and cast leaf. The process to form homogenized tobacco material sheets commonly comprises a step in which tobacco powder and a binder, are mixed to form a slurry. The slurry is then used to create a tobacco sheet. For example by casting a viscous slurry onto a moving metal belt to produce so called cast leaf. Alternatively, a slurry with low viscosity and high water content can be used to create reconstituted tobacco in a process that resembles paper-making.
The sheet material of tobacco can be referred to as a reconstituted sheet material and formed using particulate tobacco or a particulate tobacco blend, a humectant and an aqueous solvent to form the tobacco composition.
The homogenized tobacco sheet may include, in addition to the tobacco, a binder. The binder may be guar. The homogenized tobacco sheet may also include an aerosol-former. The aerosol-former may be glycerin.
The term "aerosol-forming substrate" refers to a substrate that is capable of releasing volatile compounds that may form an aerosol. Typically, aerosol-forming substrates release volatile compounds upon heating. The aerosol-forming substrate may include the material containing alkaloids containing volatile alkaloids flavor compounds, which are released from the aerosol-forming substrate upon heating. The aerosol-forming substrate may include homogenized material. The aerosol-forming substrate may include homogenized tobacco material.
As used herein, the term "aerosol-generating device" refers to a device configured to interact with an aerosol-forming substrate to generate aerosol. Preferably, the aerosol-generating device includes an aerosolizer, such as a heater.
The sheet of material containing alkaloids is thus a sheet which is formed in a material which contains any alkaloid or a combination of more than one alkaloid. The width of the sheet of material containing alkaloids is preferably greater than about 10 millimeters, more preferably greater than about 20 millimeters or about 30 millimeters. Even more preferably, the width of the sheet of material containing alkaloids is comprised between about 60 millimeters and about 2500 millimeters. The thickness of the sheet of material containing alkaloids is preferably comprised between about 50 micrometers and about 300 micrometers, more preferably the thickness of the sheet is comprised between about 100 micrometers and about 250 micrometers, even more preferably between about 130 micrometers and 220 micrometers.
The sheet of material containing alkaloids may be used as aerosol-forming substrate for an aerosol generating device.
The slurry may comprise a number of different components or ingredients. These components may influence the properties of the cast sheet of material containing alkaloids. A first ingredient is a material containing alkaloids, for example in powder form. This material can be for example a tobacco powder blend. Preferably the tobacco powder blend contains the majority of the tobacco present in the slurry. This way, the tobacco powder blend is the source of the majority of tobacco in the homogenized tobacco material. As such, the tobacco powder blend defines the flavor to the final product, for example to an aerosol produced by heating the homogenized tobacco material. The amount of tobacco powder in the slurry is preferably comprised between about 20 percent and about 45 percent of the total mass of the slurry, that is, of the mass of the slurry including water. More preferably, the amount of tobacco powder in the slurry is preferably comprised between about 25 percent and about 45 percent of the total mass of the slurry, that is, of the mass of the slurry including water.
A binder is preferably added to the slurry, in order to enhance the tensile properties of the homogenized sheet. An aerosol former is preferably added to the slurry to promote the formation of aerosol. Further, in order to reach a certain viscosity and moisture for casting the web of material containing alkaloids, water may be added to the slurry.
The quantity of binder added to the slurry may be comprised between about 0 percent and about 1 percent of the total mass of the slurry, that is, of the mass of the slurry including water. More preferably, the quantity of binder added to the slurry is comprised between about 0 percent and about 0.5 percent. The binder used in the slurry may be any of the gums or pectins described herein. The binder may ensure that the alkaloid powder remains substantially dispersed throughout the sheet of material containing alkaloids. Although any binder may be employed, preferred binders are natural pectins, such as fruit, citrus or tobacco pectins; guar gums, such as hydroxyethyl guar and hydroxypropyl guar; locust bean gums, such as hydroxyethyl and hydroxypropyl locust bean gum; alginate; starches, such as modified or derivitized starches; celluloses, such as methyl, ethyl, ethylhydroxymethyl and carboxymethyl cellulose; tamarind gum; dextran; pullalon; konjac flour; xanthan gum and the like. The particularly preferred binder for use in the present invention is guar.
Suitable aerosol-formers for inclusion in slurry for sheet of material containing alkaloids are known in the art and include, but are not limited to: monohydric alcohols like menthol, polyhydric alcohols, such as triethylene glycol, 1,3-butanediol and glycerine; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate.
Examples of preferred aerosol-formers are glycerine and propylene glycol.
The slurry may have an aerosol-former content comprised between about 1 percent and about 5 percent of the total mass of the slurry, that is, of the mass of the slurry including water. Preferably, it is comprised between 1 and 3 percent of the total mass of the slurry that correspond to an amount of aerosol-former comprised between about 2.9 percent and about 8.5 percent on a dry weight basis of the slurry.
Water is also preferably present in the slurry. The amount of water is preferably comprised between about 30 percent and 55 percent of the total mass of the slurry, that is, of the mass of the slurry including water. More preferably, the amount of water is comprised between about 45 percent and about 55 percent of the total mass of the slurry, that is, of the mass of the slurry including water.
The material containing alkaloids, preferably in powder form, may contain cellulose. However, preferably, there are no added cellulose fibres in the slurry, that is, besides the fibres already contained in the material containing alkaloids, no further fibres are added in the slurry. Therefore, the amount of added (that is, in addition to those already contained in the material containing alkaloids) fibres to the slurry is preferably lower than 0.5 percent of the total mass of the slurry, that is, of the mass of the slurry including water. More preferably, the added fibres are present in a quantity lower than about 0.1 percent of the total mass of the slurry.
The slurry is formed in a given location. The slurry may be then stored. The slurry can be for example stored and formed in the same location, for example in the same storing tank, or in two different locations, for example in two different storing tanks. The storing tank used is preferably known in the field. Further, the slurry can be formed or stored in a single storing tank, or in a plurality of storing tanks. Preferably, in the storing tank, a mixer is present to homogenize the slurry.
From the storing tank, the slurry is transferred to an extruder. The slurry is introduced for example in an inlet of the extruder, extruded, and it exits the extruder at an outlet of the same. More than one inlet and more than one outlet of the extruder may be present. The extruder might include a screw, the rotation of which may causes the compression of the slurry. A heating element may be present in the extruder to heat the slurry. The rotation of the screw may also cause the heating of the slurry. The extruder may include a single screw extruder. Extrusion here therefore may include compressing the slurry by means of a screw. Due to the compression, the slurry is directed towards the outlet of the extruder. The slurry after extrusion is still in slurry form. Preferably, the extrusion step reduces the viscosity of the slurry.
In the present context, the term "extrusion" is used in its general meaning, that is, "to force or press out; expel". The slurry after extrusion still remains in slurry form.
The extruded slurry is collected in a tank having an outlet. Preferably, the tank has a bottom wall and the outlet is formed in the bottom wall. Preferably, the outlet includes an aperture formed in the bottom wall of the tank. The tank may be located below the extruder. The tank may be integral to the extruder.
Therefore, two configurations may be present. In a first configuration, the slurry is introduced in a container. The container contains a screw which compresses the slurry towards an oulet. The container and the screw may be considered the extruder. The compressed slurry exiting the container is the introduced in a tank. From an outlet of the tank, or from a plurality of outlets of the tank, the slurry is supplied to the substrate sheet, or more than one substrate sheet.
In a second configuration, the screw is included in the tank. In other words, the tank is part of the extruder and the screw is located inside the tank. The slurry is introduced in the tank. The slurry is then compressed by the screw. Tank and screw forms the extruder. The compressed slurry exits the tank from an outlet, or a plurality of outlets, of the tank. From the outlet of the tank, the slurry is supplied to the substrate sheet or more than one substrate sheet.
In both configuration, the slurry is outputted from the outlet, or plurality of outlets, of the tank.
Further, a substrate sheet including fibres is provided. The substrate sheet defines a surface on which the slurry is supplied from the tank. The surface may be horizontal, that is, parallel to an horizontal plane, or tilted. It may also be substantially vertical. The substrate sheet may be provided in bobbin which is unwound.
The substrate sheet moves along a transport direction.
Preferably the tank including the outlet is positioned above the substrate sheet. More preferably, the outlet is located above the substrate sheet.
A substrate sheet including fibres typically is a relatively "strong" sheet, the tensile strength of which is such that it can be transported between rollers, without the need of any additional substrate on which it has to be in contact with. The tensile strength of the substrate sheet is preferably comprised between about 0.1 Newton/(millimetres)² and about 1 Newton/(millimetres)².
The substrate sheet may be made of different materials, natural or synthetic, including cellulose, hemp, kenaf, bamboo pulp, cotton, silk, or combination thereof. The selection of the material is done according to the mechanical properties expected for the final sheet including a material containing alkaloids.
The fibres' content in the substrate sheet is preferably lower than 50 grams/(meter)².
Cellulose fibres forming the sheet are preferably known in the art and may include, but are not limited to: soft-wood fibres, hard wood fibres, jute fibres, flax fibres, tobacco fibres and combination thereof. In addition to pulping, the cellulose fibres might be subjected to suitable processes such as refining, mechanical pulping, chemical pulping, bleaching, sulphate pulping and combination thereof. Cellulose fibres may include tobacco stem materials, stalks or other tobacco plant material. Preferably, cellulose fibres such as wood fibres comprise a low lignin content. Alternatively fibres, such as vegetable fibres, may be used either with the above fibres or in the alternative, including hemp and bamboo.
The substrate sheet including fibres comprises fibres having preferably a mean fibre length comprised between about 0.7 millimetres and about 50 millimetres. More preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1 millimetres and about 25 millimetres. More preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1 millimetres and about 10 millimetres. More preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1 millimetres and about 5 millimetres. Even more preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1.2 millimetres and about 1.8 millimetres.
The mean length of the fibers refers to their real length (regardless whether they are curled or have kinks) as measured by MORFI COMPACT commercialised by Techpap SAS. The mean length is the mathematical mean of the measured length of the fibers by MORFI COMPACT over a measurement of N fibers, where N > 5. The MORFI COMPACT is a fiber analyser that measures the length of the fibers following the framework of the fibers, thus measuring their real developed length. Measured objects are considered fibers if their length is comprised between 200 microns and 10000 microns and their width is comprised between 5 microns and 75 microns. Fibers length is measured when deionized water is added to the fibers and Morfi software is used.
The fibres in the substrate sheet may be woven or not woven. If not woven, the fibres may be oriented predominantly in one direction. Also, the fibres may be for example randomly oriented. If woven, various patterns could be used.
The substrate sheet defines a first surface and a second surface. For example, the frist surface or the second surface may be substantially planar surface. The first surface and the second surface may be, one opposite to the other. In order to apply or distribute the slurry present in the tank to the first surface of the substrate sheet, the substrate sheet is preferably moved, so that the slurry is applied to the first surface along its length, forming a strip of slurry on the substrate sheet including fibres.
The slurry does not need to be applied to the whole first surface. The slurry can be applied only to part of the first surface, for example to a central portion of the first surface.
Preferably, therefore, the substrate sheet is moved along the transport direction, such as for example linearly moved, and a part of the first surface of the substrate sheet enters into contact with the slurry.
The slurry which comes into contact with the substrate sheet may be completely absorbed by the substrate sheet. The slurry may form a coating on the first surface of the substrate sheet. The slurry may also be partly absorbed by the substrate sheet and partly coat the first surface of the substrate sheet. The resulting sheet formed by the substrate sheet and the slurry may have a different composition in a cross section taken perpendicularly to the first surface of the substrate sheet. At the second surface, the lowest amount of slurry may be present. At the first surface, the highest amount of slurry may be present. In between, a combination of substrate sheet's material and slurry may be present in different concentrations.
In order to move the substrate sheet along the transport direction, a moving element may be provided. The moving element may include a movable support and the substrate sheet including fibres may be positioned on the movable support, so that the movable support, while moving, transports the substrate sheet.
In another embodiment, the moving element may include a moving drum, which - in its rotation - moves the substrate sheet. The support sheet may be free standing for a portion of its length.
The amount of slurry in the tank is preferably kept substantially constant. For example, the amount of slurry in the tank is equal to a pre-defined quantity. Preferably, the pre-defined quantity of amount of slurry in the tank is maintained constant. For example, a pre-determined level of slurry within the tank is set. In order to obtain a substantially constant level of slurry in the tank, slurry is continuously supplied to the tank while the slurry is supplied onto the substrate sheet. The level of slurry in the tank may be checked by means of a sensor and the amount of slurry provided by the extruder into the tank may be varied to maintain the level in the tank constant.
As said, from the outlet of the tank, the slurry is supplied onto the substrate sheet. The slurry forms a deposit on the substrate sheet's first surface.
Further, due to the movement of the substrate sheet in the transport direction, the slurry supplied from the outlet forms a strip of slurry. The combination of substrate sheet and a strip of slurry provided on its first surface forms a sheet of material containing alkaloids.
In addition to the substrate sheet and the strip of slurry, other elements may be combined in order to form the sheet of material containing alkaloids. The substrate sheet itself may be a multilayered sheet. The substrate sheet may include a flavor sheet, a sheet of material comprising nicotine, and others.
Forming a sheet of material containing alkaloids supplying slurry onto an already formed substrate sheet including fibres allows to use substantially no added fibres in the slurry. Fibres are commonly added in the slurry in order to increase the tensile strength of the sheet, acting as a strengthening agent.
However, the presence of a substrate sheet on which the slurry is supplied provides sufficient tensile strength to the resulting sheet of material containing alkaloids. The cellulose fibres addition into the slurry may be avoided.
In slurry where fibres are added, a relatively high amount of water may be required in the slurry, because water is needed for the fibres pulping. In addition, due to the large amount of water present in the slurry, a high amount of energy is needed in order to dry the slurry and form a sheet of the material containing alkaloids. In this "high water content" process, the conveyor steel belt on which the slurry is casted may also play an important role: any imperfection in the conveyor belt may be transferred to the cast sheet, thus a high quality belt is often required. Removing the fibres from the slurry allows to decrease the amount of water which is needed to homogenize the slurry. A certain amount of water may still be needed for good homogenization. This amount of water may be further reduced afterwards by means of the extrusion process. This relatively "dense" slurry is suitable to be applied to the substrate sheet including fibres.
Less drying time or less drying power is required for drying the sheet of material including alkaloids produced according to the invention. The substrate sheet is preferably already dried when it is wound in a bobbin. The substrate sheet may be wetted, for example spraying water on it, before contacting the slurry. The wetting is done to facilitate the penetration of the slurry in the substrate sheet. The resulting multilayered sheet of material containing alkaloids or sheet of composite material containing alkaloids is only "partly wet" and the drying time or the required amount of energy for drying is comparatively low. A less "intense" drying allows to have a better control on the flavour of the aerosol produced by the sheet of material containing alkaloids when used as an aerosol forming substrate. During drying, alkaloids, flavours or other volatiles may evaporate and their concentration in the sheet of material containing alkaloids may be reduced. Minimizing the drying when the alkaloids are present helps to control the aerosol characteristics. Smaller dryers may be required compared to those used for drying cast leaf. Energy may be saved. Floor space may be saved.
Preferably, all outlets of the plurality are formed on the bottom wall of the tank. Due to the plurality of outlets, more than a single slurry strip may be created. A single substrate sheet including fibres may be provided, on which a number of slurry' strips equal to the number of outlets formed on the tank is supplied. The single substrate sheet having on its surface a plurality of strip of slurry may be cut in sub-sheets. Alternatively, a single slurry strip may be formed on the substrate sheet and other slurry strips may be formed elsewhere. The substrate sheet therefore may comprise one, or more than one, strip of slurry. Preferably, the plurality of strips of slurry are parallel to each other.
For example, if the movable support is present, a strip of slurry may be formed on the substrate sheet and a strip of slurry may be formed on the movable support.
The step of supplying slurry from the plurality of outlets comprises the step of: supplying slurry from the plurality of outlets on more than one substrate sheets including fibres, to form more than one sheet of material containing alkaloids. Preferably, more than one sheet of material containing alkaloids is formed at the same time. More than one substrate sheet including fibres is provided. The number of substrate sheets may be equal or different to the number of outlets formed in the tank. Therefore, in each substrate sheet either a single strip of slurry may be formed, or more than one strip of slurry, or no strip of slurry. A single strip of slurry may be formed if the number of substrate sheets is equal to the number of outlets formed in the tank. More than one strip of slurry may be formed if the number of substrate sheet is lower than the number of outlets. A slitting step of a "wide" sheet of material containing alkaloids in narrower sheets may be avoided. The process requires less components, such as a slitting blade. The machine, such as the dryer, may be smaller.
Further, also in the case in which the number of substrate sheets is equal to the number of outlets in the tank, the substrate sheets may be so positioned that on some substrate sheets no slurry is supplied, while on other substrate sheets more than one strip of slurry is formed.
In case of more than one substrate sheet, the substrate sheets may be identical to each other. In particular, the substrate sheets may all have the same thickness. The substrate sheets may all have the same width.
Preferably, the thickness of the substrate sheet is comprised between about 175 micrometers and about 250 micrometers. More preferably, the thickness of the substrate sheet is comprised between about 190 micrometers and about 220 micrometers. Preferably the width of the substrate sheet is comprised between 100 millimetres and 150 millimetres.
Preferably, the step of supplying slurry from the plurality of outlets comprises spraying the slurry onto the substrate sheet. Preferably, the step of supplying slurry from the plurality of outlets comprises spraying the slurry onto at least one of the more than one substrate sheet. Preferably, the step of supplying slurry from the plurality of outlets comprises spraying the slurry onto all of the more than one substrate sheet. Preferably, a nozzle ejects the slurry from the tank onto the substrate sheet, preferably on a surface of the substrate sheet including fibres, preferably on the surfaces of the more than one substrate sheet. The slurry present in the tank may be highly viscous, for example it may have a dynamic viscosity comprised between about 18000 Centipoises and about 45000 Centipoises and for this reasons preferably one or more pumps are provided in order to push the slurry towards the outlets of the tank. Preferably, a nozzle is positioned at each outlet.
Preferably, the step of supplying slurry from the plurality of outlets comprises depositing the slurry on the substrate sheet. Preferably, the step of supplying slurry from the plurality of outlets comprises depositing the slurry on at least one of the more than one substrate sheet. Preferably, the step of supplying slurry from the plurality of outlets comprises depositing the slurry on all of the more than one substrate sheet. The supply of slurry on the substrate sheet may take place by gravity only. A roller may be positioned at each outlet. The roller may be in contact with the substrate sheet including fibres. The slurry falls from the tank into the outlet and then on the roller by gravity. In this way, the roller coats the substrate sheet, or the more than one substrate sheet, with slurry.
Preferably, the method comprises the step of: regulating the pressure or the flow rate of the slurry supplied from the outlet. Preferably, the method comprises the step of: regulating the pressure or the flow rate of the slurry supplied from at least one outlet of the plurality of outlets. Preferably, the method comprises the step of: regulating the pressure or the flow rate of the slurry supplied from all outlets of the plurality. Even more preferably, the step of regulating the pressure or the flow rate of the slurry supplied from the outlet includes: regulating the pressure or the flow rate of the slurry supplied from at least one outlet of the plurality of outlets independently from at least one of the other outlets of the plurality of outlets. Given N outlets, and selected an outlet among the N available, the pressure or flow rate of the slurry exiting the selected outlet is independent from at least one of the pressure or flow rate of the slurry exiting the other N-1 outlets. Preferably, the pressure of flow rate of the slurry is independently regulated at all outlets of the plurality of outlets. Preferably, at least one outlet of the plurality of outlets includes a pump to regulate the pressure or the flow rate of the slurry exiting the outlet. More preferably, each outlet of the plurality of outlets includes a pump to regulate the pressure or the flow rate of the slurry exiting the outlet. Preferably, both the pressure and the flow rate may be regulated at each outlet independently from at least another outlet of the plurality of outlets.
Preferably, the method comprises the step of reducing the amount of water in the slurry while extruding. Preferably, the method comprises the step of reducing the amount of water in the slurry while compressing the slurry with a screw. During the extrusion process, the amount of water in the slurry may be reduced. This is due for example to the heat and pressure present during the extrusion process. Reducing the water in the slurry may allow to obtain a more dense slurry that, when supplied to the substrate sheet, needs less time and energy to dry. In this way, a control of the resulting flavour and alkaloids concentration in the resulting sheet of material containing alkaloids may be obtained. Preferably, the amount of water removed during the extrusion is less than about 50 percent of the total mass of the slurry. Preferably, the amount of water removed during the extrusion is less than about 25 percent of the total mass of the slurry. Preferably, the amount of water removed during the extrusion is less than about 15 percent of the total mass of the slurry. Preferably, the amount of water removed during the extrusion is greater than about 2 percent of the total mass of the slurry. More preferably, the amount of water removed during the extrusion is greater than about 4 percent of the total mass of the slurry.
After the extrusion, the amount of binder (in weight) remains substantially the same as before the extrusion. After the extrusion, the amount of aerosol former (in weight) remains the same as before the extrusion. After the extrusion, the amount of material containing alkaloids (in weight) remains the same as before the extrusion. After the extrusion, preferably, the amount of water decreases from between about 30 percent and about 55 percent of the total mass of the slurry before the extrusion to about between 30 percent and 50 percent of the total mass of the slurry.
Preferably, the method comprises the step of orienting a flow of slurry supplied from one or more of the outlets of the plurality with a component along a direction of movement of the substrate sheet. Preferably, the outlets of the tank have a specific shape. At least one outlet of the plurality of outlets may include a pipe or a nozzle having a curvature. For example, the pipe or nozzle may have an arched configuration. Preferably, a curved nozzle is provided. This curvature is adapted to impart to the slurry flow flowing out of the pipe or nozzle a component different from zero along an axis parallel to the transport direction of the substrate sheet.
Preferably, the method comprises the step of evaluating the thickness of the sheet of material containing alkaloids. Preferably, the method comprises the step of evaluating the thickness of at least one sheet of the more than one sheet of material containing alkaloids. Preferably, the method comprises the step of evaluating the thickness all of the more than one sheet of material containing alkaloids. Preferably, the method comprises the step of compressing the sheet of material containing alkaloids. Preferably, the method comprises the step of compressing at least one of the more than one sheet of material containing alkaloids. Preferably, the method comprises the step of compressing all of the more than one sheet of material containing alkaloids. More preferably, the method comprises the step of changing the thickness of the sheet of material containing alkaloids by compressing the sheet of material containing alkaloids. More preferably, the method comprises the step of changing the thickness of the sheet of material containing alkaloids by compressing at lest one of the more than one sheet of material containing alkaloids. More preferably, the method comprises the step of changing the thickness of the sheet of material containing alkaloids by compressing all of the more than one sheet of material containing alkaloids. The compression step may include a calendaring step. The compression step may be performed inserting the sheet of material containing alkaloids between two compressing rollers. The thickness of the sheet may be checked after the slurry has been deposited and dried. The thickness of the sheet may be measured by optical sensors. Suitable optical sensors may include X-ray sensors or laser sensors or a combination thereof. If the measured thickness is outside a desired range, a feedback loop may be provided in order to correct the thickness of the sheet.
Preferably, the step of providing a slurry including a material containing alkaloids, an aerosol former and water comprises at least one of: providing the material containing alkaloids to the slurry in an amount comprised between about 40 percent and about 70 percent of the total weight of the slurry; providing the water to the slurry in an amount comprised between about 30 percent and about 55 percent of the total weight of the slurry; providing a binder to the slurry in an amount comprised between about 0 percent and about 1 percent of the total weight of the slurry; or providing the aerosol former to the slurry in an amount comprised between 1 percent and about 5 percent of the total weight of the slurry.
More preferably, the step of providing the material containing alkaloids to the slurry comprises providing the material containing alkaloids to the slurry in an amount comprised between about 40 percent and about 50 percent of the total weight of the slurry.
More preferably, the step of providing the water to the slurry comprises providing the water to the slurry in an amount comprised between about 45 percent and about 55 percent of the total weight of the slurry. Due to the relatively low amount of water in the sheet of material containing alkaloids, a relatively low drying time is required compared to the cast sheet. A minimal loss of volatiles from the sheet may be achieved.
More preferably, the step of providing a binder to the slurry comprises providing the binder to the slurry in an amount comprised between about 0 percent and about 0.5 percent of the total weight of the slurry. The amount of binder may depend on the desired characteristics of the sheet of material containing alkaloids. If it is desired that the slurry is greatly absorbed by the substrate sheet, then less binder may be used to improve absorption. If a slurry coating on the substrate sheet is preferred, a higher amount of binder may be used. The amount of binder may vary the viscosity of the slurry. A higher amount of binder may lead to a higher viscosity of the slurry.
More preferably, the step of providing an aerosol former to the slurry comprises providing the aerosol former to the slurry in an amount comprised between 1 percent and about 3 percent of the total weight of the slurry.
Preferably, the step of providing a slurry including a material containing alkaloids, an aerosol former and water comprises the step of: grinding a material containing alkaloids to a powder having a size comprised between about 8 microns and 200 microns. More preferably, the step of providing a slurry including a material containing alkaloids, an aerosol former and water comprises the step of: grinding a material containing alkaloids to a powder having a size comprised between about 10 microns and 150 microns. Even more preferably, the step of providing a slurry including a material containing alkaloids, an aerosol former and water comprises the step of: grinding a material containing alkaloids to a powder having a size comprised between about 15 microns and 120 microns. Due to the fact that the slurry does not contain, or contain a very small amount, of cellulose fibres in addition of those already contained in the material containing alkaloids, the size of the powder does not need to be "extremely small". In order to obtain an homogeneous slurry, particles of material containing alkaloids are preferably "small". The small size is also due to the absence of added fibres which act as "glue" in a cast leaf. Preferably, the size of the grinded particles of material containing alkaloids have a size smaller than 200 microns, preferably smaller than 180 microns, preferably smaller than 160 microns, preferably smaller than 140 microns, preferably smaller than 120 microns, preferably smaller than 100 microns, preferably smaller than 80 microns, preferably smaller than 60 microns, preferably smaller than 40 microns. Preferably, the size of the grinded particles of material containing alkaloids have a size larger than 8 microns, preferably larger than 12 microns, preferably larger than 20 microns, preferably larger than 30 microns, preferably larger than 50 microns, preferably larger than 70 microns.
With size of the particle of the material containing alkaloids, the Dv95 size is meant. Each of the values above listed indicates the Dv95 of the particle size. The "v" in Dv95 means that a volume distribution is considered. The use of volume distributions introduces the concept of the equivalent sphere. An equivalent sphere is a sphere which is equal to the real particle in the property which we are measuring. Thus for light scattering methods, it is a sphere which would produce the same scattering intensities as the real particle. This is substantially a sphere having the same volume of the particle. Further, "95" in Dv95 means the diameter where ninety-five percent of the distribution has a smaller particle size and five percent has a larger particle size. Thus the particle size is that size according to a volume distribution where 95 percent of the particles have a diameter (of the corresponding sphere having substantially the same volume of the particle) smaller than the stated value. A particle size of 60 microns means that 95 percent of the particles have a diameter smaller than 60 microns, where the diameter is the diameter of the sphere having a corresponding volume than the particle.
The Dv95 size of the particle is measured using a Horiba LA 950 or LA 960 particle size distribution analyser. The HORIBA LA-960 particle size analyser uses the laser diffraction method to measure size distributions. This technique uses first principles to calculate size using light scattered off the particle (edge diffraction) and through the particle (secondary scattering refraction). The LA-960 incorporates the Mie scattering theory.
Further, the viscosity of the slurry may depend on the size of the powder of the material containing alkaloids. The larger the size, the more viscous the slurry may become.
Preferably, the method comprises a step of providing the substrate sheet with fibres having an mean fibre length comprised between about 0.7 millimetres and about 50 millimetres. Preferably, the method comprises a step of providing at least one of the more than one substrate sheet with fibres having an mean fibre length comprised between about 0.7 millimetres and about 50 millimetres. Preferably, the method comprises a step of providing all of the more than one substrate sheet with fibres having an mean fibre length comprised between about 0.7 millimetres and about 50 millimetres. More preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1 millimetres and about 25 millimetres. More preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1 millimetres and about 10 millimetres. More preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1 millimetres and about 5 millimetres. Even more preferably, the fibres of the substrate sheet including fibres have a mean fibre length comprised between about 1.2 millimetres and about 1.8 millimetres.
Preferably, the substrate sheet is a braided sheet. A braided sheet is a sheet where the fibres are intertwined. Not all fibres need to be intertwined, but a fraction thereof. A braided sheet allows to obtain an homogeneous and relatively high mechanical strength.
Preferably, the step of extruding the slurry and collecting the extruded slurry in a tank having a plurality of outlets comprises: extruding the slurry by means of a screw. Preferably, the extrusion of the slurry takes place in a single screw extruder. Single screw extrusion creates pressure in the slurry. This forces the extrusion of the slurry. Single screw extruders can either be used as part of a large extrusion system or used as stand-alone machine for extrusion. The screw may be located within a hot barrel. As the screw turns, it moves the slurry within the hot barrel. In this way, the slurry reaches the required temperatures as well as mixes thoroughly to form a slurry that is homogenous. The pressure which is built up by the single screw extruders then forces the slurry from the extruder. Extrusion includes compressing the slurry by means of a screw. More preferably, the step of extruding includes the step of inserting the slurry in a single screw extruder. The process is still considered to be extrusion although at the outlet of the extruder slurry comes out. The tank may be part of the extruder or external to the extruder.
Preferably, the method comprises the step of: homogenizing the extruded slurry collected in the tank. The slurry coming out of the extruder enters into the tank. Alternatively, the tank is part of the extruder and the extruded slurry collects in a portion of the tank where it is extruded. In the tank, the slurry is preferably mixed or otherwise stirred. Stirring or mixing may improve the homogeneity of the slurry. Preferably, the slurry is made uniform in structure or composition throughout. Therefore, the composition of the slurry and its characteristics, such as viscosity and temperature, are the same throughout the tank. In this way, the slurry supplied by the plurality of outlets is substantially the same from every outlet. If more than one sheet of material containing alkaloids is formed by the method of the invention, all sheets have substantially the same characteristics because the slurry outputted from the outlets has the same characteristics (assuming that a plurality of identical substrate sheets is used).
Preferably, the step of supplying the slurry from the plurality of outlets so as to form a plurality of parallel strips of slurry includes: providing a moving drum located below the plurality of outlets; unwinding one or more bobbins so as to obtain one or more substrate sheets including fibres; placing the one or more substrate sheets including fibres onto the moving drum so as to move the one or more substrate sheets along a direction of movement; and supplying slurry from the plurality of outlets on the one or more substrate sheets including fibres while the one or more substrate sheets including fibres are moved along the direction of movement by the moving drum. Preferably, the step of supplying the slurry from the plurality of outlets so as to form a plurality of parallel strips of slurry includes: providing a moving drum located below the plurality of outlets; unwinding more than one bobbin so as to obtain more than one substrate sheet including fibres; placing the more than one substrate sheet including fibres onto the moving drum so as to move the more than one substrate sheet along a direction of movement; and supplying slurry from the plurality of outlets on the more than one substrate sheet including fibres while the more than one substrate sheets including fibres are moved along the direction of movement by the moving drum.
Preferably, the one or more substrate sheet are self-supporting. The rotation of the moving drum in turnmoves the one or more substrate sheets. No conveyor belt is needed to support the substrate sheets once the movement is imparted. The one or more substrate sheets including fibres, are capable of being "self-supporting". Preferably, the second surface of the one or more substrate sheets opposite to the first surface facing the outlets of the tank is - at least for a length interval - not in contact with any further element. The substrate sheet, after being supplied with slurry, may travel "free standing", with both surface free from contacts with any other element. The fact that a conveyor belt is substantially not needed any more to support the sheet of material containing alkaloids, allows more flexibility on the overall system. In processes where the slurry is casted on a conveyor belt, a conveyor belt having strict dimensional requirements is generally required. Such a belt, when self-supporting substrate sheets are used, may not be necessary anymore.
Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a schematic perspective view of an apparatus for production of a sheet of a material containing alkaloids according to the invention;
Figure 2 shows a front view of the apparatus of Figure 1;
Figure 3 shows a lateral view of the apparatus of figure 1 and 2; and
Figure 4 shows an enlarged view of a detail of the apparatuses of figures 1-3.

With initial reference to figures 1 and 2, an apparatus for the production of a sheet of a material containing alkaloids 200 according to the present invention is represented and indicated with reference number 100.
The apparatus 100 is adapted for the production of a plurality of sheets of material containing alkaloids 200. In this embodiment, the plurality of sheets are sheets of homogenized tobacco material.
The apparatus 100 for the production of a sheet of homogenized tobacco material includes an extruder 2, a tank 3 positioned at an outlet 20 of the extruder 2 and a moving drum 4 located below the tank 3.
The extruder 2 comprises an inlet 21 where slurry 22 (indicated by an arrow in figure 1) to form the sheet of homogenized tobacco material is introduced, a screw 23 to extrude the slurry, and the outlet 20. The slurry 22 is pushed by the screw 23 from the inlet to the outlet 20 (see again arrows 22). The screw 23 pushing the slurry 22 may be rotated by a motor 24 (see for example figure 2).
Slurry 22 reaches the extruder 2 from a different storing tank or silo, not shown in the appended drawings. Slurry 22 comprises tobacco powder, water, a binder and an aerosol former. Preferably the binder is guar. Preferably, the aerosol former is glycerine. Preferably, no further fibres are added in the slurry.
Slurry 22 at the inlet has the following composition in total mass

Water: 30 % - 55 %
Tobacco powder: 40 % - 70%
Binders: 0 % -1 %
Aerosol -former: 1 % - 5 %
Added fibres: less than 0.5 %

From the extruder 2, the slurry 22 reaches the tank 3. From the above composition, a 5 % of water is removed from the slurry by the extrusion process.
The tank 3 comprises a plurality of outlets all indicated with 30. Tank 3 may have any geometrical shape, and in the depicted embodiment it is substantially a basin. Tank 3 includes lateral walls 32 and also further includes a bottom wall 33. A mixer 34 (indicated by an arrow in figure 1) can be present inside the tank 3 to stir and mix the slurry.
Further, a sensor 50 is present in the tank 3 to measure the vertical level of the slurry. Preferably, a feedback is present between the sensor 30 and the extruder 2 so that the slurry is kept in the tank 3 at a substantially constant level.
Below outlet 30, the moving drum 4 is located. Moving drum 4 is adapted to rotate around its axis 6 in a direction of rotation 5 indicated by an arrow in figures 1 and 2. Moving drum 4 defines an external cylindrical surface 41.
Further, the apparatus 100 includes a plurality of bobbins 7. Each bobbin 7 of the plurality is made of coils of a substrate sheet 8, for example a cellulose fibres sheet. The bobbin is unwound and the free portion of the sheet 8 unwound from the bobbin 7 is positioned in contact with moving drum 4. The substrate sheet 8 includes a first and a second surface 11, 1, one opposite to the other. The second surface 1 is preferably in contact with cylindrical surface 41 of the moving drum 4. The first surface 11 faces at least one of the plurality of outlets 30. The rotation of the moving drum 4 causes a movement of the plurality of substrate sheets 8 along a common transport direction, indicated with arrow 12 in figure 1 and 3. The bobbins 7 are thus continuously unwound by the rotation of drum 4.
Each substrate sheet 8 of the plurality is in contact with the surface 41 of the moving drum 4 and, downstream the drum 4 along the transport direction, is free standing, that is, the first and second surfaces 11, 1 are not supported by any element. A further drum or roller (not visible in the drawing) may further pull the plurality of sheets 8 in the transport direction 12.
From the outlets 30, the slurry 22 is supplied to the plurality of substrate sheets 8. Preferably, each outlet 30 of the plurality of outlets 8 supplies slurry 22 to a single substrate sheet 8 of the plurality of sheets, as visible in figure 2. The slurry is delivered from the outlets 30 by gravity or applying pressure, for example by means of pump 31. Slurry from tank 3 is transferred from tank 3 to the substrate sheets 8 through the plurality of outlets 30 by means of pump 31. Preferably pump 31 comprises a control (not visible in the drawing) of flow rate to control the amount of slurry delivered to the substrate sheet 8.
When the substrate sheet is supplied with slurry 22, it becomes a homogenized tobacco sheet 200. The slurry may be absorbed by the substrate sheet 8 partly or completely. Most of the slurry may coat the substrate sheet 8, in particular the second surface 11.
In an embodiment, in the bottom wall 33 of the tank 3 a plurality of apertures 35 is formed, each aperture connected to a pipe 36 (see figures 2 and 3). A valve 37 regulates the flow of slurry through the pipe 36. Downstream the valve 37, in the direction of flow of the slurry, the pipe 36 ends into outlet 30.
In a different embodiment, not shown, a plurality of apertures is formed directly to the bottom wall 16 and a plurality of pipes is connected, each pipe to a different aperture, without the presence of valves.
Each pipe 37 terminates with a nozzle 38 where the outlet 30 is present, as visible in figure 3 and 4. The nozzle 38 is a curved nozzle, having a horizontal inlet 39 and the outlet 30 from which the slurry exits forming a flow having a component along the transport direction 12.
As better visible in figure 2, the number of substrate sheets 8 is equal to the number of outlets 30. The substrate sheets are all in contact with surface 41 of drum 4 with their second surfaces 1. The width 42 of each substrate sheet 8 is preferably equal to the width of the standard "small bobbins" (for example preferably between about 10 millimetres and about 300 millimetres) used for further processing the sheets 200. The width 42 of all substrate sheets 8 is preferably the same.
Further, preferably additional sensors (not shown) are arranged at the substrate sheet 200 downstream the outlets 30 to measure the weight per square centimetre and the thickness of the homogenized tobacco sheets 200. The sensor may be for example a nucleonic measuring head. Additional sensors, snot shown in the drawings, are preferably present as well, such as a sensor to locate and determine the positions of defects in the sheet of homogenized tobacco, a sensor to determine the moisture of the sheets 200, a sensor to measure a thickness of the sheet, a sensor to check the alignment of the sheets in order to avoid misaligned and jammed sheets in case more than a sheet is formed.
The functioning of the apparatus 100 for forming the plurality of homogenized tobacco sheets 200 is as follows. Slurry 22, formed preferably mixing and combining tobacco powder, water and other ingredients, preferably with no or low content of added fibres, is transferred from a storing tank (not shown) using for example in line mixers (also not shown) to the extruder 2. The slurry reduces its water contents at the extruders 2 and it is extruded inside the tank 3. In tank 3, valves 36 are opened and the slurry reaches outlets 30, with or without the needs of pump 31. Nozzles 38 supplies slurry onto substrate sheet 8 including fibres which are positioned in contact to moving drum 4. Movements of drum 4 causes the shifts of substrate sheets 8 along transport direction 12. Each nozzle 38 deposits slurry on a different substrate sheet 8. A plurality of homogenized tobacco sheets 200 is thus formed.
The thickness of the sheets 200 and grammage controlled by nucleonic gauge immediately after slurry supply are preferably continuously monitored and feedback-controlled using slurry measuring device.

Claims

Method for the production of a sheet (200) of a material containing alkaloids, the method comprising the steps of:
- providing a slurry (22) including a material containing alkaloids, an aerosol former and water;

- extruding the slurry (22);

- collecting the extruded slurry (22) in a tank (3) having a plurality of outlets (30);

- providing more than one substrate sheet (8) including fibres;

- supplying slurry (22) from the plurality of outlets (30) so as to form a plurality of strips of slurry on the more than one substrate sheet (8) including fibres, to form more than one sheet (200) of material containing alkaloids.
Method according to one or more of the preceding claims, wherein the step of supplying slurry (22) from the plurality of outlets (30) comprises:
- spraying the slurry (22) onto at least one substrate sheet (8), or

- depositing the slurry (22) on at least one substrate sheet (8).
Method according to any of the preceding claims, comprising the step of:
- regulating the pressure or the flow rate of the slurry (22) supplied from at least one outlet (30) of the plurality.
Method according to claim 3, wherein the step of regulating the pressure or the flow rate of the slurry (22) supplied from the at least one outlets (30) of the plurality includes regulating the pressure or the flow rate of the slurry supplied from at least one outlet (30) of the plurality of outlets (30) independently from at least one of the other outlets (30) of the plurality of outlets (30).
Method according to any of the preceding claims, comprising the step of:
- reducing the amount of water in the slurry while extruding.
Method according to one or more of the preceding claims, comprising the step of:
- orienting a flow of slurry (22) supplied from at least one outlet (30) of the plurality with a component along a direction of movement (12) of the substrate sheet (8).
Method according to one or more of the preceding claims, comprising the step of:
- evaluating the thickness of at least one of the more than one sheet (200) of material containing alkaloids; and

- changing the thickness of at least one of the more than one the sheet (200) of material containing alkaloids by compressing the at least one of the more than one sheet (200) of material containing alkaloids in case the evaluated thickness is outside a given range of values.
Method according to one or more of the preceding claims, wherein providing a slurry (22) including a material containing alkaloids, an aerosol former and water comprises at least one of:
- providing the material containing alkaloids to the slurry (22) in an amount comprised between about 40 percent and about 70 percent of the total weight of the slurry (22);

- providing the water to the slurry (22) in an amount comprised between about 30 percent and about 55 percent of the total weight of the slurry (22);

- providing a binder to the slurry (22) in an amount comprised between about 0 percent and about 1 percent of the total weight of the slurry (22); or

- providing the aerosol former to the slurry (22) in an amount comprised between 1 percent and about 5 percent of the total weight of the slurry (22).
Method according to one or more of the preceding claims, wherein the step of providing a slurry (22) including a material containing alkaloids, an aerosol former and water comprises the step of:
- grinding a material containing alkaloids to a powder having a size comprised between about 8 microns and 200 microns.
Method according to one or more of the preceding claims, comprising the step of providing at least one of the more than one substrate sheet (8) including fibres having a mean fibre length comprised between about 0.7 millimetres and about 2.5 millimetres.
Method according to one or more of the preceding claims, comprising the step of:
- homogenizing the extruded slurry (22) collected in the tank (3).
Method according to one or more of the preceding claims, wherein supplying the slurry (22) from the plurality of outlets (30) so as to form a plurality of parallel strips of slurry (22) includes:
- providing a moving drum (4) located below the plurality of outlets (30), the moving drum (4) rotating around an axis (6);

- providing more than one bobbin (7) of substrate sheet (8);

- unwinding the more than one bobbin (7) so as to obtain more than one substrate sheet (8) including fibres;

- placing the more than one substrate sheet (8) including fibres in contact with the moving drum (4) so as to move the more than one substrate sheet (8) along a direction of movement due to the moving drum's (4) rotation;

- supplying slurry (22) from the plurality of outlets (30) on the more than one substrate sheet (8) including fibres while the more than one substrate sheet (8) including fibres are moved along the direction of movement (12) by the moving drum (4).
A system for the production of more than one sheet (200) of material containing alkaloids, the system comprising:
- more than one bobbin (7) of a substrate sheet (8) including fibres;

- an apparatus (100) for supplying slurry (22) to the more than one substrate sheet (8) including fibres, the apparatus (100) comprising:
i. an extruder (2) adapted to extrude a slurry (22);

ii. a tank (3) having a plurality of outlets (30) adapted to contain the slurry (22); and

iii. a moving element adapted to move the more than one substrate sheet (8) including fibres unwound from the more than one bobbin (7) along a transport direction (12) and under the outlet (30), so that slurry (22) is applied to the more than one substrate sheet (8).
The system according to claim 13, wherein the extruder (2) is a screw extruder.